A054007 Numbers k such that k and k+1 have the same sum but an unequal number of divisors.

206, 957, 1364, 2974, 4364, 14841, 18873, 19358, 20145, 24957, 36566, 56564, 74918, 79826, 79833, 92685, 111506, 116937, 138237, 147454, 161001, 162602, 174717, 190773, 193893, 201597, 230390, 274533, 347738, 416577, 422073, 430137

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..8304 (terms below 10^13, calculated from the b-file at A002961)

Formula

Members of A002961 which are not members of A054004

Example

The divisors of 206 are 1, 2, 103, 206, so tau(206) = 4 and sigma(206) = 312; the divisors of 207 are 1, 3, 9, 23, 69, 207, so tau(207) = 6 and sigma(207) = 312. Hence, the integer 206 belongs to this sequence. - Bernard Schott, Oct 18 2019

Mathematica

Select[Range[100000], DivisorSigma[0, #] != DivisorSigma[0, # + 1] && DivisorSigma[1, #] == DivisorSigma[1, # + 1] &] (* Jayanta Basu, Mar 20 2013 *)

Crossrefs

Cf. A000005, A000203, A002961, A005237, A053249, A054004, A054005, A054006.

Sequence in context: A113934 A260101 A113490 * A285754 A201032 A133149

Adjacent sequences: A054004 A054005 A054006 * A054008 A054009 A054010

Keyword

nonn

Author

Asher Auel, Jan 12 2000

Extensions

More terms from Jud McCranie, Oct 15 2000

Status

approved